Short chain carboxylic acids of C2 to C5 carbon atoms in length have a wide range of applications, including from serving as monomers for polymers, paints, and coatings, to fragrance sources for perfumes and other commodities. Currently, such carboxylic acids are produced mainly from petrochemical sources. For example, propionic acid, which is routinely used in making preservatives and polymers, is produced by carbonylation of ethylene. Similarly, acetic acid is produced by carbonylation of methanol or by oxidation of ethylene. Thus, the production of short chain carboxylic acids depends heavily on the petrochemical industry and may become limited in near future due to the depletion of fossil fuels. Further, the production of carboxylic acids from such sources may also lead to other serious issues, such as environmental pollution and global warming, as a result of excess CO2 emissions.
Alternative methods for producing carboxylic acids in industry include fermentation by microorganisms and hydrothermal oxidation. For example, the fermentation of glycerol and other carbohydrate biomass leads to the production of propionic acid. Certain microorganisms such as C. Tyrobutyricum produce butyric acid as an end-product by fermentation, with acetic acid as a minor by-product. However, the efficiency of such processes is low and is highly dependent on the type and the quality of raw biomass used. Although there have been reports on the production of acetic acid from hydrothermal oxidation of carbohydrates, the yield of acetic acid is minimal and needs to be enhanced. Thus, there remains a need to identify alternative sources for producing these carboxylic acids, and developing methods for producing short chain carboxylic acids from carbohydrate biomass with high efficiency is desirable.